Tuesday, November 22, 2016

Season 9 superfinal, games 27-36

After 36 games Stockfish leads 7-2 with 27 draws. There have been 9 draws in the last 10 games, draw rate is increasing to 75%. At this level this is to be expected even with careful opening choices, we wouldn't want really one-sided openings that cannot be defended.
We are still waiting for a decision on Game 17.

Game 27 started with a small eval advantage for Stockfish. There were many early exchanges and at move 23 only RB vs RN left. Stockfish was up a pawn with an ugly looking pawn structure. Evals were at 1, can Stockfish get something out of the ending?

After exchanging rooks the central group of doubled pawns became strong, it guaranteed a pawn majority in the center and it was an obstacle for Houdini's pieces. Evals were gradually rising, Stockfish thought it was doing well.

At this point Houdini was having trouble finding moves to play. Its king side pawns could not advance, its king and knight had to keep an eye on the white pieces. Stockfish attempted to get its king to g4 to help its pawns advance. Houdini countered with the c pawn and forced the white king back to the center. The c pawn became another target to defend and Houdini's pieces were already overworked. Houdini was forced to allow Stockfish to play f5 but then its position collapsed. After capturing the c pawn Stockfish's king could infiltrate the king side winning the game. Well played endgame by Stockfish.
In the reverse game more pieces remained on the board. Houdini had a bishop pair against Stockfish's knight pair, both kings were a little exposed to attack. Houdini kept a small eval advantage, Stockfish's eval dropped to 0 when a series of exchanges simplified to a RBB vs RR position. When Stockfish captured the last white pawn and gave a rook for a bishop the RB vs R ending was a draw.

In game 29 the engines exchanged almost all pieces after the opening, reaching a rook endgame on move 24. Stockfish had a small eval advantage for another 10 moves, but there was no real advantage on the board resulting in a short draw.
In the reverse game the engines kept a few more pieces on the board, reaching a QRN vs QRN position on move 25. After queens were exchanged Stockfish's eval dropped to 0. Houdini remained optimistic much longer, it traded 3 pawns for the black knight but with no pawns left it couldn't win.

Stockfish did not castle in game 31, a locked pawn line in the center made its king relatively safe. Houdini's king side pawns were far from the king and Stockfish used an open g file to make attack threats. In the end both Stockfish's threats on the king side nor Houdini's counter on the queen side were effective, the engines exchanged rooks and simplified to a QBN vs QBB position. Evals dropped nearly to 0 and a draw was agreed.
In game 32 the engines exchanged almost all the queen side pawns, Houdini castled late to find safety for its king. When the f file opened the engines placed their rooks there, leading to the rooks being exchanged. Then the game reached a BB vs BN ending with evals close to 0 and another draw.

Game 33 reached a RRB vs RRB position by move 24. Stockfish had a small eval advantage for a few more moves, but after exchanging a pair of rooks and with opposite color bishops the evals fell quickly to 0. Stockfish had to give the bishop to stop a black pawn, still a draw.
In game 34 Stockfish's eval reached 0 even faster on move 16, though there seemed to be a lot of potential in the game. Houdini lost a rook for a knight but got an active attack on Stockfish's exposed king. The game was heading for a 3-fold check repetition when Stockfish changed its mind. The draw was achieved after the queens were exchanged, Houdini won back the material reaching a drawn rook ending.

There were many exchanges after the opening of game 35, and at move 30 only QB vs QN remained. Stockfish had a small eval advantage, yet it was Houdini that had a passer in the center. Houdini's king was more exposed and Stockfish used checks to drive it to the queen side and then capture pawns on the king side. Houdini had two queen side passers to counter Stockfish's 3 to 1 pawn advantage on the king side. Here Houdini played for a draw, it blocked the white pawns, found a protected spot for its knight and defended with its queen and king. Stockfish could not break this defense and after 30 moves it gave up and agreed to a draw.
Game 36 also started with many exchanges, after move 21 only QRB vs QRB remained. Houdini won a pawn while Stockfish continued to simplify, reaching an opposite color bishop ending. One pawn was not enough and Houdini couldn't break through the black line with all the black pawns invisible to its bishop. It took 70 moves for the engines to stop their shuffling and declare a draw.

That's 4 straight openings with only draw results. Is Stockfish playing defensively waiting for the match to end? Can Houdini close the gap? Still many games to go.